1. Field of the Invention
The present invention relates to an apparatus for measuring body composition of a human body, based on bioelectrical impedance measurement, and more particularly, to construction of a handgrip for such apparatus adapted for making contact with a body of a person under test for collecting the living body information. The handgrip is generally incorporated into any measuring apparatus based on the bioelectrical impedance measurement. Such measuring apparatus then derives the body information of the person, such as those including a body fat percentage representing a rate of fat relative to the total weight of the person and an amount of body fat representing the weight of the fat.
2. Description of the Prior Art
It is already known to estimate body composition of a human body from the measurement of living body impedance. For instance, it has been found in an article xe2x80x9cAssessment of fat-free mass using bioelectrical impedance measurement of the human bodyxe2x80x9d, The American Journal of Clinical Nutrition, 41 (4) 810-817, 1985. This principle of operation may be applied to measure the amount of body fat for a person under test. For instance, any impedance between extreme parts of the person such as hands and feet may be measured according to four-terminal electrode measurement theory. The impedance thus measured, together with the personal body information such as the weight, height, sex and age of the person under test, can be used to estimate the amount of body fat for the person. TOKUKOUHEI No. 5-49050 discloses an apparatus for measuring the weight of a person under test concurrent with the amount of body fat. A various types of apparatus utilizing such principle have already been put into the market.
A body fat measuring apparatus based on such bioelectrical impedance measurement is constructed in such manner that electrodes are directly made contact with a skin of a person. Then very small AC current is actually passed through the body of the person for measuring the body fat percentage and the amount of body fat for the person. Therefore, the measuring apparatus includes the electrodes adapted for contact with the specified parts of the person under test to get the living body information.
Such electrodes are generally designed to contact with a sole or a palm of the person. In case of the electrode to contact with the sole, it is mounted on the measuring apparatus and the person under test can make contact with the electrode at substantially constant pressure under the weight of the person. On the other hand, for the electrode to contact with the palm, it is constructed for the person to grasp a handgrip on which the electrode is mounted. Therefore, depending on how to grasp the handgrip or how to apply the force thereto by the person under test, the measuring conditions would be greatly changed.
For instance, TOKUKAIHEI No. 11-178806 discloses a grip, as shown in FIG. 6 of the accompanying drawings. Referring to FIG. 6, this grip is substantially in the form of a cylinder in which an applying electrode 73 and a measuring electrode 74 are disposed spaced apart to each other along the longitudinal axis of the cylinder. The applying electrode 73 applies a high frequency signal through a palm of a person under test who grasps the grip 72.
The measuring electrode 74 is mounted for measuring a potential across the body resistance also through the palm of the person who grasps the grip 72. The grip 72 is detachably connected to the main measuring apparatus via an electric wire 75.
A recess 72A is formed between the applying electrode 73 and the measuring electrode 74 for placing the middle finger of the person.
More specifically, when the person under test grasps the grip 72, he grasps an upper grip section 72B on which the applying electrode 73 is mounted with his index and thumb fingers. At the same time, he grasps a lower grip section 72C on which the measuring electrode 74 is mounted with his medical and little fingers.
Furthermore, in order not to wrongly grasp the upper and lower grip sections by the person, the lower grip section 72C is formed longer than: the upper grip section 72B in the axial direction.
For instance, the upper grip section 72B has the length equal to the width of one finger plus some margin, but the lower grip section 72C has the length equal to the width of two fingers plus some margin. In this way, if the person wrongly grasps the grip upside down, he would find this fact due to unusual feeling in grasping. Then the person re-grasps the grip correctly.
The lower grip section 72C further includes a projected portion 77 extending on a plane on which the palm of the person makes contact with the grip 72. The projected portion 77 acts to achieve good close contact of the palm with the measuring electrode 74.
More particularly, because of the lower grip section 72C only grasped with the medical and little fingers of the person, the grasping force applied thereby is lower than that for the upper grip section 72B. This does not achieve good close contact of the palm with the measuring electrode 74, and therefore, there may be any possibility that no reliable measurement can be attained. In order to solve such problem, the projected portion 77 is provided to assure the good close contact of the palm with the measuring electrode, irrespective of lower grasping force.
In the grip as shown in FIG. 6, the middle finger of the person is placed in the recess 72A, as described above. This means that other fingers of the person are limited in their contact positions on the grip. The diameter of the grip is fixed, and therefore, it is difficult to reliably hold the grip with the sufficient force by all the people from an adult whose hands are large to a child whose hands are small. Accordingly the grip in FIG. 6 can not always attain the desired stable contact condition for different persons under test.
Although not shown here, other handgrips known in the art are constructed in the same manner as above. Therefore, they can not easily be grasped by everybody and can attain no stable contact condition.
In view of the above, the present invention aims at providing a new and improved handgrip for use in bioelectrical impedance measurement, that allows the measurement always under a stable contact condition, irrespective of the size of a hand of the person under test. Further the present invention aims at providing a body fat measuring apparatus operated based upon the bioelectrical impedance measurement using the handgrip.
To attain those objects, the present invention provides a bioelectrical impedance measuring apparatus provided with a handgrip, a current source for supplying a measuring current into a body of a person under test via a current supplying electrode in contact with palm of the person, a voltage measuring unit for measuring a voltage on a voltage measuring electrode, and an arithmetic unit for calculating a bioelectrical impedance of the person based said current and said voltage, comprising the handgrip including a cylindrical grip section on which said current supplying electrode and said voltage measuring electrode are disposed each in parallel to an axis of said grip section, said cylindrical grip section gradually increasing in diameter from a portion thereof that is in contact with a thumb and a index fingers of the person toward a portion thereof that is in contact with a little finger of the person.
Preferably the handgrip further includes an auxiliary member coupled with said cylindrical grip section.
Preferably said current supplying electrode is disposed on a portion of the grip section that is contact with finger tips of the person in parallel to the axis of said grip section. In addition said voltage measuring electrode is disposed on a portion of the grip section that is contact with a palm and a thenar of the person in parallel to the axis of said grip section.
Preferably said current supplying electrode and said voltage measuring electrode are provided on each of a pair of handgrips for right and left hands of the person.